Chris, if I read Sagawa's "Tomei na Chikara", if I'm not mistaken, there's a part that says Takeda Sokaku Dai-sensei learned martial arts from Saigo Tanomo. Some people said Saigo's the adviser, but hey, that time, "advisor" is really your tutor, right?

Also the story that says AIR is a fellow koryu from Aizu area, where Takeda Dai-sensei came from, by using common sense, isn't that obvious that Takeda Sokaku Dai-sensei also learnt that skill, especially since he's from a samurai family.